The School of Ocean Sciences at Bangor University, the National Oceanography Centre and HR Wallingford have published two new peer-reviewed research papers in Nature Portfolio journals, advancing understanding of how offshore wind infrastructure and climate change are reshaping the seabed. Both research papers are available to read here: “Climate change affects future sea-bed mobility via storms and sea level rise” and “Turbulence drives seabed modification by offshore windfarms”
Both studies are outcomes of the project ECOWind-ACCELERATE (short for “Ecological Implications of Accelerated Seabed Mobility around Windfarms”), a project led by Bangor University, and as part of the ECOWind programme funded by the Natural Environment Research Council (NERC) and The Crown Estate.
The most recent paper, published in Nature Communications and led by Dr Chris Unsworth, finds that the hydrodynamic forces driving sediment mobility in the wake of offshore wind turbine foundations are stronger and extend further than previously recognised.
Seabed sediments (sand, mud, and gravel) determine which species can survive or thrive in a given area. Using a combination of laboratory experiments, computer models, and real-world data from an operating windfarm, the research shows that turbulence caused by monopile foundations can disturb sediments across 3–8% of the seabed within a typical windfarm. This effect from turbulence is not included in current estimates of seabed modification, which are approximately 1% of the wind farm area. As offshore wind capacity expands rapidly to meet low-carbon energy goals, accurately quantifying these effects is essential.
Dr. Chris Unsworth, senior scientist at HR Wallingford and formerly of Bangor University, said, “Whilst we are good at estimating scour at a monopile (and other infrastructure), the effect of the flow field on the seabed further away had been overlooked; yet this larger turbulent effect on sediment mobility has the potential to change seabed composition and habitats. In this paper we have developed and validated a new method to do just this.”
Dr Thomas Benson, Technical Director at HR Wallingford, added, “The approach we took was to adapt a Reynolds-averaged Navier-Stokes model (openTELEMAC) to include the effects of turbulence on the seabed. The efficiency of this approach compared to a full Navier-Stokes model means we can simulate the turbulence generated by the monopiles across a large spatial domain and over a sufficiently long timescale to provide a better understanding of the impacts of the wake effects on the seabed.”
This study closely follows the publication of a paper in Communications Earth & Environment led by Dr Julia Rulent. Julia is a Coastal Ocean Modelling Scientist at the National Oceanography Centre, and this study examines how climate change is also altering seabed sediment dynamics. Using advanced computer models and climate projections, this research shows that rising sea levels will generally stabilise seabed sediments by increasing water depth and therefore reducing the effects of waves and currents. However, stronger storms are expected to cause more frequent short-term disturbances, and pebbles will move in the future in areas where they would not move today.
Dr Julia Rulent notes: “It is important to quantify seabed disturbance from regular tides and rare storms. By knowing both the baseline natural processes, and how they could change in future, we have meaningful context for human impacts from seabed infrastructure.”
Together the two studies provide examples for separating the environmental impacts of wind energy infrastructure from those of the broader climate crisis.
Professor Katrien Van Landeghem from the School of Ocean Sciences at Bangor University leads the ECOWind-ACCELERATE project. She said: “These rigorously peer-reviewed studies show how collaborative research is advancing our understanding of the effects of climate change and offshore wind development on seabed environments. The findings support future-proof environmental assessments of rapidly changing seas, and risk-informed planning for e.g. subsea cables or habitat restoration. As seabed mobility shapes marine habitats and food webs, responsible offshore wind development must be accompanied by strong environmental stewardship.”
